Controlling build chamber temperature

ABSTRACT

A build chamber of a three-dimensional printer uses directed heat to preheat a region within the chamber where a build will be initiated, and then uses circulating, heated air to maintain a target temperature for the entire build volume after the build is initiated. A fixed heating element and blower may advantageously be used for both heating steps, and preheating may be accomplished more quickly by initially directing heat at the locus of build initiation rather than diffusing heat throughout an entire build volume.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.14/147,567 filed Jan. 5, 2014, the entire content of which is herebyincorporated by reference.

FIELD OF THE INVENTION

This document generally relates to a device and method for controllingbuild chamber temperature, and more specifically controlling buildchamber temperature in a device and system for three-dimensionalfabrication.

BACKGROUND

Certain additive manufacturing techniques such as three-dimensionalprinting use thermoplastics or the like that can be deposited in aheated, liquid form and then cooled to provide a resulting solidstructure. Some systems use a heated build chamber in order to mitigatethermal stresses and other difficulties that arise from the thermalexpansion and contraction of build materials during fabrication. Whilethe heated build chamber usefully regulates the thermal environment fora build process, there is typically a significant amount of heatinginefficiency, particularly early in the fabrication process when only asmall amount of build material requires any thermal management. Thereremains a need for improved heating techniques that direct initialheating toward the region(s) in a build chamber where a build will beinitiated.

SUMMARY

A build chamber of a three-dimensional printer uses directed heat topreheat a region within the chamber where a build will be initiated, andthen uses circulating, heated air to maintain a target temperature forthe entire build volume after the build is initiated. A fixed heatingelement and blower may advantageously be used for both heating steps,and preheating may be accomplished more quickly by initially directingheat at the locus of build initiation rather than diffusing heatthroughout an entire build volume.

In one aspect, a device includes a build chamber of a three-dimensionalprinter, where the build chamber includes a build region where a buildis initiated. The device further includes a heater and a blower thatmoves air at a variable flow rate in response to a control signal. Theblower is positioned to move the air over the heater toward the buildregion. Additionally, the device includes a sensor that provides asensor signal indicative of a temperature of the build region, and acontroller that varies the control signal in response to the sensorsignal. The control signal drives the blower at a first flow rate topreheat the build region before initiating the build, and the controlsignal drives the blower at a second flow rate, which may be greaterthan the first flow rate, to heat the build chamber after initiating thebuild.

In general, in another aspect, a method includes providing apredetermined temperature for initiating a build in a build region of abuild chamber of a three-dimensional printer. The method furtherincludes preheating the build region to the predetermined temperature bydirecting air with a blower at a first flow rate over a heater andtoward the build region. Additionally, the method includes initiatingthe build when the build region reaches the predetermined temperature,and heating the build chamber by directing the air with the blower at asecond flow rate over the heater, where the second flow rate may begreater than the first flow rate.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention will be apparent from the following description of particularembodiments thereof, as illustrated in the accompanying drawings. Thedrawings are not necessarily to scale, emphasis instead being placedupon illustrating the principles of the devices and methods describedherein.

FIG. 1 is a block diagram of a three-dimensional printer.

FIG. 2 is a perspective view of a three-dimensional printer.

FIG. 3 is a perspective view of a three-dimensional printer.

FIG. 4 is a perspective view of a blower and heater.

FIG. 5 is a flow chart illustrating a method for controlling a buildchamber temperature.

FIG. 6 is a block diagram illustrating a temperature control system.

DETAILED DESCRIPTION

The embodiments will now be described more fully hereinafter withreference to the accompanying figures, in which preferred embodimentsare shown. The foregoing may, however, be embodied in many differentforms and should not be construed as limited to the illustratedembodiments set forth herein. Rather, these illustrated embodiments areprovided so that this disclosure will convey the scope to those skilledin the art.

All documents mentioned herein are hereby incorporated by reference intheir entirety. References to items in the singular should be understoodto include items in the plural, and vice versa, unless explicitly statedotherwise or clear from the text. Grammatical conjunctions are intendedto express any and all disjunctive and conjunctive combinations ofconjoined clauses, sentences, words, and the like, unless otherwisestated or clear from the context. Thus, the term “or” should generallybe understood to mean “and/or” and so forth.

Recitation of ranges of values herein are not intended to be limiting,referring instead individually to any and all values falling within therange, unless otherwise indicated herein, and each separate value withinsuch a range is incorporated into the specification as if it wereindividually recited herein. The words “about,” “approximately,” or thelike, when accompanying a numerical value, are to be construed asindicating a deviation as would be appreciated by one of ordinary skillin the art to operate satisfactorily for an intended purpose. Ranges ofvalues and/or numeric values are provided herein as examples only, anddo not constitute a limitation on the scope of the describedembodiments. The use of any and all examples, or exemplary language(“e.g.,” “such as,” or the like) provided herein, is intended merely tobetter illuminate the embodiments and does not pose a limitation on thescope of the embodiments. No language in the specification should beconstrued as indicating any unclaimed element as essential to thepractice of the embodiments.

In the following description, it is understood that terms such as“first,” “second,” “top,” “bottom,” “side,” “front,” “back,” and thelike, are words of convenience and are not to be construed as limitingterms.

Described herein are devices, systems, and methods for controlling thebuild chamber temperature for a three-dimensional printer such as any ofthe printers described in commonly-owned U.S. Pat. Nos. 8,282,380 &8,425,218, the entire contents of which are hereby incorporated byreference. It will be understood that while the exemplary embodimentsherein emphasize controlling the build chamber temperature for athree-dimensional printer, the principles of this disclosure may beadapted to other fabrication processes. All such variations that can beadapted to use a device, system, and method for controlling a buildchamber temperature as described herein are intended to fall within thescope of this disclosure.

FIG. 1 is a block diagram of a three-dimensional printer. In general,the printer 100 may include a build platform 102, a conveyor 104, anextruder 106, an x-y-z positioning assembly 108, and a controller 110that cooperate to fabricate an object 112 within a working volume 114 ofthe printer 100.

The build platform 102 may include a surface 116 that is rigid andsubstantially planar. The surface 116 may support the conveyer 104 inorder to provide a fixed, dimensionally and positionally stable platformon which to build the object 112.

The build platform 102 may include a thermal element 130 that controlsthe temperature of the build platform 102 through one or more activedevices 132 such as resistive elements that convert electrical currentinto heat, Peltier effect devices that can create a heating or coolingeffect, or any other thermoelectric heating and/or cooling devices. Thusthe thermal element 130 may be a heater that provides active heating tothe build platform 102, a cooling element that provides active coolingto the build platform 102, or a combination of these. The heater 130 maybe coupled in a communicating relationship with the controller 110 inorder for the controller 110 to controllably impart heat to or removeheat from the surface 116 of the build platform 102. Thus, the thermalelement 130 may include an active cooling element positioned within oradjacent to the build platform 102 to controllably cool the buildplatform 102.

It will be understood that a variety of other techniques may be employedto control a temperature of the build platform 102. For example, thebuild platform 102 may use a gas cooling or gas heating device such as avacuum chamber or the like in an interior thereof, which may be quicklypressurized to heat the build platform 102 or vacated to cool the buildplatform 102 as desired. As another example, a stream of heated orcooled gas may be applied directly to the build platform 102 before,during, and/or after a build process. Any device or combination ofdevices suitable for controlling a temperature of the build platform 102may be adapted to use as the thermal element 130 described herein.

The conveyer 104 may be formed of a sheet 118 of material that moves ina path 120 through the working volume 114. Within the working volume114, the path 120 may pass proximal to the surface 116 of the buildplatform 102—that is, resting directly on or otherwise supported by thesurface 116—in order to provide a rigid, positionally stable workingsurface for a build. It will be understood that while the path 120 isdepicted as a unidirectional arrow, the path 120 may be bidirectional,such that the conveyer 104 can move in either of two opposing directionsthrough the working volume 114. It will also be understood that the path120 may curve in any of a variety of ways, such as by looping underneathand around the build platform 102, over and/or under rollers, or arounddelivery and take up spools for the sheet 118 of material. Thus, whilethe path 120 may be generally (but not necessarily) uniform through theworking volume 114, the conveyer 104 may move in any direction suitablefor moving completed items from the working volume 114. The conveyor mayinclude a motor or other similar drive mechanism (not shown) coupled tothe controller 110 to control movement of the sheet 118 of materialalong the path 120. Various drive mechanisms are described in furtherdetail below.

In general, the sheet 118 may be formed of a flexible material such as amesh material, a polyamide, a polyethylene terephthalate (commerciallyavailable in bi-axial form as MYLAR), a polyimide film (commerciallyavailable as KAPTON), or any other suitably strong polymer or othermaterial. The sheet 118 may have a thickness of about three to aboutseven thousandths of an inch, or any other thickness that permits thesheet 118 to follow the path 120 of the conveyer 104. For example, withsufficiently strong material, the sheet 118 may have a thickness ofabout one to about three thousandths of an inch. The sheet 118 mayinstead be formed of sections of rigid material joined by flexiblelinks.

A working surface of the sheet 118 (e.g., an area on the top surface ofthe sheet 118 within the working volume 114) may be treated in a varietyof manners to assist with adhesion of build material to the surface 118and/or removal of completed objects from the surface 118. For example,the working surface may be abraded or otherwise textured (e.g., withgrooves, protrusions, and the like) to improve adhesion between theworking surface and the build material.

A variety of chemical treatments may be used on the working surface ofthe sheet 118 of material to further facilitate build processes asdescribed herein. For example, the chemical treatment may include adeposition of material that can be chemically removed from the conveyer104 by use of water, solvents, or the like. This may facilitateseparation of a completed object from the conveyer by dissolving thelayer of chemical treatment between the object 112 and the conveyor 104.The chemical treatments may include deposition of a material that easilyseparates from the conveyer such as a wax, mild adhesive, or the like.The chemical treatment may include a detachable surface such as anadhesive that is sprayed on to the conveyer 104 prior to fabrication ofthe object 112.

In one aspect, the conveyer 104 may be formed of a sheet of disposable,one-use material that is fed from a dispenser and consumed with eachsuccessive build.

In one aspect, the conveyer 104 may include a number of differentworking areas with different surface treatments adapted for differentbuild materials or processes. For example, different areas may havedifferent textures (smooth, abraded, grooved, etc.). Different areas maybe formed of different materials. Different areas may also have orreceive different chemical treatments. Thus a single conveyer 104 may beused in a variety of different build processes by selecting the variousworking areas as needed or desired.

The extruder 106 may include a chamber 122 in an interior thereof toreceive a build material. The build material may, for example, includeacrylonitrile butadiene styrene (“ABS”), high-density polyethylene(“HDPL”), polylactic acid, or any other suitable plastic, thermoplastic,or other material that can usefully be extruded to form athree-dimensional object. The extruder 106 may include an extrusion tip124 or other opening that includes an exit port with a circular, oval,slotted or other cross-sectional profile that extrudes build material ina desired cross-sectional shape.

The extruder 106 may include a heater 126 to melt thermoplastic or othermeltable build materials within the chamber 122 for extrusion through anextrusion tip 124 in liquid form. While illustrated in block form, itwill be understood that the heater 126 may include, e.g., coils ofresistive wire wrapped about the extruder 106, one or more heatingblocks with resistive elements to heat the extruder 106 with appliedcurrent, an inductive heater, or any other arrangement of heaterssuitable for creating heat within the chamber 122 to melt the buildmaterial for extrusion. The extruder 106 may also or instead include amotor 128 or the like to push the build material into the chamber 122and/or through the extrusion tip 124.

In general operation (and by way of example rather than limitation), abuild material such as ABS plastic in filament form may be fed into thechamber 122 from a spool or the like by the motor 128, melted by theheater 126, and extruded from the extrusion tip 124. By controlling arate of the motor 128, the temperature of the heater 126, and/or otherprocess parameters, the build material may be extruded at a controlledvolumetric rate. It will be understood that a variety of techniques mayalso or instead be employed to deliver build material at a controlledvolumetric rate, which may depend upon the type of build material, thevolumetric rate desired, and any other factors. All such techniques thatmight be suitably adapted to delivery of build material for fabricationof a three-dimensional object are intended to fall within the scope ofthis disclosure. Other techniques may be employed for three-dimensionalprinting, including extrusion-based techniques using a build materialthat is curable and/or a build material of sufficient viscosity toretain shape after extrusion.

The x-y-z positioning assembly 108 may generally be adapted tothree-dimensionally position the extruder 106 and the extrusion tip 124within the working volume 114. Thus by controlling the volumetric rateof delivery for the build material and the x, y, z position of theextrusion tip 124, the object 112 may be fabricated in three dimensionsby depositing successive layers of material in two-dimensional patternsderived, for example, from cross-sections of a computer model or othercomputerized representation of the object 112. A variety of arrangementsand techniques are known in the art to achieve controlled linearmovement along one or more axes. The x-y-z positioning assembly 108 may,for example, include a number of stepper motors 109 to independentlycontrol a position of the extruder within the working volume along eachof an x-axis, a y-axis, and a z-axis. More generally, the x-y-zpositioning assembly 108 may include without limitation variouscombinations of stepper motors, encoded DC motors, gears, belts,pulleys, worm gears, threads, and the like. Any such arrangementsuitable for controllably positioning the extruder 106 within theworking volume 114 may be adapted to use with the printer 100 describedherein.

By way of example and not limitation, the conveyor 104 may be affixed toa bed that provides x-y positioning within the plane of the conveyor104, while the extruder 106 can be independently moved along a z-axis.As another example, the extruder 106 may be stationary while theconveyor 104 is x, y, and z positionable. As another example, theextruder 106 may be x, y, and z positionable while the conveyer 104remains fixed (relative to the working volume 114). In yet anotherexample, the conveyer 104 may, by movement of the sheet 118 of material,control movement in one axis (e.g., the y-axis), while the extruder 106moves in the z-axis as well as one axis in the plane of the sheet 118.Thus in one aspect, the conveyor 104 may be attached to and move with atleast one of an x-axis stage (that controls movement along the x-axis),a y-axis stage (that controls movement along a y-axis), and a z-axisstage (that controls movement along a z-axis) of the x-y-z positioningassembly 108. More generally, any arrangement of motors and otherhardware controllable by the controller 110 may serve as the x-y-zpositioning assembly 108 in the printer 100 described herein. Still moregenerally, while an x, y, z coordinate system serves as a convenientbasis for positioning within three dimensions, any other coordinatesystem or combination of coordinate systems may also or instead beemployed, such as a positional controller and assembly that operatesaccording to cylindrical or spherical coordinates.

The controller 110 may be electrically coupled in a communicatingrelationship with the build platform 102, the conveyer 104, the x-y-zpositioning assembly 108, and the other various components of theprinter 100. In general, the controller 110 is operable to control thecomponents of the printer 100, such as the build platform 102, theconveyer 104, the x-y-z positioning assembly 108, and any othercomponents of the printer 100 described herein to fabricate the object112 from the build material. The controller 110 may include anycombination of software and/or processing circuitry suitable forcontrolling the various components of the printer 100 described hereinincluding without limitation microprocessors, microcontrollers,application-specific integrated circuits, programmable gate arrays, andany other digital and/or analog components, as well as combinations ofthe foregoing, along with inputs and outputs for transceiving controlsignals, drive signals, power signals, sensor signals, and the like. Inone aspect, the controller 110 may include a microprocessor or otherprocessing circuitry with sufficient computational power to providerelated functions such as executing an operating system, providing agraphical user interface (e.g., to a display coupled to the controller110 or printer 100), convert three-dimensional models into toolinstructions, and operate a web server or otherwise host remote usersand/or activity through the network interface 136 described below.

A variety of additional sensors may be usefully incorporated into theprinter 100 described above. These are generically depicted as sensor134 in FIG. 1, for which the positioning and mechanical/electricalinterconnections with other elements of the printer 100 will depend uponthe type and purpose of the sensor 134 and will be readily understoodand appreciated by one of ordinary skill in the art. The sensor 134 mayinclude a temperature sensor positioned to sense a temperature of thesurface of the build platform 102. This may, for example, include athermistor or the like embedded within or attached below the surface ofthe build platform 102. This may also or instead include an infrareddetector or the like directed at the surface 116 of the build platform102 or the sheet 118 of material of the conveyer 104. Other sensors thatmay be usefully incorporated into the printer 100 as the sensor 134include a heat sensor, a volume flow rate sensor, a weight sensor, asound sensor, and a light sensor. Certain more specific examples areprovided below by way of example and not of limitation.

The sensor 134 may include a sensor to detect a presence (or absence) ofthe object 112 at a predetermined location on the conveyer 104. This mayinclude an optical detector arranged in a beam-breaking configuration tosense the presence of the object 112 at a location such as an end of theconveyer 104. This may also or instead include an imaging device andimage processing circuitry to capture an image of the working volume 114and analyze the image to evaluate a position of the object 112. Thissensor 134 may be used for example to ensure that the object 112 isremoved from the conveyor 104 prior to beginning a new build at thatlocation on the working surface such as the surface 116 of the buildplatform 102. Thus the sensor 134 may be used to determine whether anobject is present that should not be, or to detect when an object isabsent. The feedback from this sensor 134 may be used by the controller110 to issue processing interrupts or otherwise control operation of theprinter 100.

The sensor 134 may include a sensor that detects a position of theconveyer 104 along the path. This information may be obtained from anencoder in a motor that drives the conveyer 104, or using any othersuitable technique such as a visual sensor and corresponding fiducials(e.g., visible patterns, holes, or areas with opaque, specular,transparent, or otherwise detectable marking) on the sheet 118.

The sensor 134 may include a heater (instead of or in addition to thethermal element 130) to heat the working volume 114 such as a radiantheater or forced hot air to maintain the object 112 at a fixed, elevatedtemperature throughout a build. The sensor 134 may also or insteadinclude a cooling element to maintain the object 112 at a predeterminedsub-ambient temperature throughout a build.

The sensor 134 may also or instead include at least one video camera.The video camera may generally capture images of the working volume 114,the object 112, or any other hardware associated with the printer 100.The video camera may provide a remote video feed through the networkinterface 136, which feed may be available to remote users through auser interface maintained by, e.g., remote hardware, or within a webpage provided by a web server hosted by the three-dimensional printer100. Thus, in one aspect there is a user interface adapted to present avideo feed from at least one video camera of a three-dimensional printerto a remote user through a user interface.

The sensor 134 may include may also include more complex sensing andprocessing systems or subsystems, such as a three-dimensional scannerusing optical techniques (e.g., stereoscopic imaging, or shape frommotion imaging), structured light techniques, or any other suitablesensing and processing hardware that might extract three-dimensionalinformation from the working volume 114. In another aspect, the sensor134 may include a machine vision system that captures images andanalyzes image content to obtain information about the status of a job,working volume 114, or an object 112 therein. The machine vision systemmay support a variety of imaging-based automatic inspection, processcontrol, and/or robotic guidance functions for the three-dimensionalprinter 100 including without limitation pass/fail decisions, errordetection (and corresponding audible or visual alerts), shape detection,position detection, orientation detection, collision avoidance, and thelike.

Other components, generically depicted as other hardware 135, may alsobe included, such as input devices including a keyboard, touchpad,mouse, switches, dials, buttons, motion sensors, and the like, as wellas output devices such as a display, a speaker or other audiotransducer, light emitting diodes, and the like. Other hardware 135 mayalso or instead include a variety of cable connections and/or hardwareadapters for connecting to, e.g., external computers, external hardware,external instrumentation or data acquisition systems, and the like.

The printer 100 may include, or be connected in a communicatingrelationship with, a network interface 136. The network interface 136may include any combination of hardware and software suitable forcoupling the controller 110 and other components of the printer 100 to aremote computer in a communicating relationship through a data network.By way of example and not limitation, this may include electronics for awired or wireless Ethernet connection operating according to the IEEE802.11 standard (or any variation thereof), or any other short or longrange wireless networking components or the like. This may includehardware for short range data communications such as BlueTooth or aninfrared transceiver, which may be used to couple into a local areanetwork or the like that is in turn coupled to a data network such asthe Internet. This may also or instead include hardware/software for aWiMax connection or a cellular network connection (using, e.g., CDMA,GSM, LTE, or any other suitable protocol or combination of protocols).Consistently, the controller 110 may be configured to controlparticipation by the printer 100 in any network to which the networkinterface 136 is connected, such as by autonomously connecting to thenetwork to retrieve printable content, or responding to a remote requestfor status or availability.

A device for controlling a build chamber temperature of athree-dimensional printer will now be described.

FIG. 2 is a perspective view of a three-dimensional printer. Thethree-dimensional printer 200 may include a build chamber 202 that issealed from the surrounding environment with a door 204 in a frontportion of the three-dimensional printer 200 and one or more viewingareas 206 in side portions of the three-dimensional printer 200. Thedoor 204 may provide access to the build chamber 202 of thethree-dimensional printer 200, e.g., in order to load, unload orotherwise handle objects and materials within the build chamber 202.However, one skilled in the art will recognize that the build chamber202 may instead be partially or completely open, and that manyconfigurations for a build chamber are possible including, but notlimited to, configurations having multiple access points to the buildchamber and configurations having fewer or more viewing areas, which mayeach be sealed or unsealed. The build chamber 202 may include a buildplatform, an extruder, and an x-y-z positioning assembly, along with anyother components described above with reference to FIG. 1.

The build chamber 202 may also include a heater 208 for heating thebuild chamber 202. The heater 208 may be disposed in a housing 210 orother ductwork with an opening 212 to direct air over a heating elementwithin the heater 208. The opening 212 may include a louvered opening asshown in FIG. 2, which may be configured to direct heated air from thehousing 210 into the build chamber 202 in one direction or a pluralityof directions. For example, heated air may be directed to a build regionof the build chamber 202 in which a build is initiated in thethree-dimensional printer 200. The build region, as used throughout thisdisclosure, may include the volume in which the build is initiatedand/or the region where the build takes place throughout athree-dimensional print (i.e., the region where the build material isextruded). Depending on the configuration of the printer 200, this buildregion may be fixed at a stationary position within the build chamber202 throughout a build (e.g., where an extruder remains stationarythroughout a build) or the build region may move on any or all of the x,y, and z axes. The opening 212 may also be adjustable (manually,automatically, or a combination thereof) in order to steer a directionof the heated air. Heated air may be moved by components (e.g.,mechanical components such as a fan) included within the housing 210 ofthe heater 208, or through components located elsewhere (e.g., otherwisedisposed in the build chamber 202, or disposed outside of the buildchamber 202).

FIG. 3 is a perspective view of a three-dimensional printer. In general,the three-dimensional printer 300 may include a build chamber 302,viewing areas 306, and a heater 308. As shown in FIG. 3, a housing forthe heater may be omitted and air may be directed over a heater 308 thatis open to the build chamber 302.

The heater 308 may include coil heaters 314 as shown, or any otherheaters known to one of ordinary skill in the art and suitable forcreating temperatures and heat transfers as contemplated herein. Theheater 308 may also or instead include a metal heater (e.g., wire,ribbon, strip, etched foil, and the like), a heat lamp (e.g., anincandescent lamp, and the like), ceramic heaters (e.g., molybdenumdisilicide, positive temperature coefficient (PTC) ceramic elements, andthe like), composite heaters (e.g., tubular heaters, screen-printedelements, and the like), combination heater systems (e.g., thick filmtechnology, and the like), or any other heater or combination of heatersknown in the art or that will be known in the art.

The three-dimensional printer 300 may also include a blower 316, whichmay be disposed near (e.g., adjacent to) the heater 308. The blower 316may include a fan (not shown in FIG. 3) and an opening 318 that directsair past the heater 308 in order to heat air moving over the heater 308.The blower 316 may also or instead include centrifugal fans, axial fans,centrifugal blowers, positive-displacement blowers, cross-flow fans,bellows, Coanda effect devices, convective devices, electrostaticdevices, or any combination of elements that can be used to create aflow of air. The devices and systems described herein may also include aplurality of blowers.

It will be understood that while a particular orientations of heaters,blowers and openings/ducting are shown in FIGS. 2 and 3, a variety ofconfigurations may also or instead usefully be employed. For example,the housing 208 of FIG. 2 is positioned on a back wall of a buildchamber 202 and oriented to direct air upward along the back wall. Thisair flow will tend to redirect from a vertical flow along the back wallto a horizontal flow along a top of the build chamber, which tendencymay be enhance by suitably shaping the upper rear edge into which theair is initially directed. This approach may be advantageously used witha build platform that is initially positioned near a top of the buildchamber and moves downward as a build progresses. Thus air from theblower will always be directed toward a region where new material isbeing deposited without requiring any active steering of air flow duringa build. At the same time, this general approach directs heated airupward, consistent with and improved by the natural upward convectioncurrent of heated air.

While this configuration usefully adapts to the natural air currentsthat result from heating, other approaches may also or instead beemployed. For example, a build platform may be positioned near a bottomof the build chamber and used with an x-y gantry that moves upward alonga z-axis during a print. In such a printer, heated air may be directeddownward along a sidewall so that air flow reflects along an edge andhorizontally inward toward the build region, or the air may be initiallydirected horizontally above and/or beneath the build platform. Air mayinitially be flowed across the build platform at a relatively low flowrate so that heated air can transfer heat to preheat a build region. Asthe build region moves upward in the layers of an object beingfabricated, air flow along the bottom may be increased (as describedbelow) to circulate air at a greater flow rate throughout the chamber.

FIG. 4 depicts an implementation of the heater 408 and blower 416, wherethe heater 408 includes coil heaters 414, and the blower 416 includes afan 420. The blower 416 may further include a curved duct 422 or similarductwork with an opening 418 directed toward the coil heaters 414.Additionally, the blower 416 may include a housing 424 that holds themechanical elements of the fan 420 that creates air flow (e.g., fanblades, motor, etc.).

The aforementioned mechanical components can be used to create a deviceand method for controlling the temperature of a build chamber of a threedimensional printer. For example, a build region where a build is to beinitiated may be preheated to a predetermined temperature beforeinitiating a build, after which the entire build chamber may bemaintained at a second predetermined temperature while the buildcompletes. An implementation includes heating the build region to thedesired build region temperature in a rapid manner. This may beaccomplished, for example by slowly moving air over the heater andtoward the build region, thus increasing the time for heat transfer tothe air, and for heat transfer from the air to the build region. Whenthe build region achieves the desired build region temperature, thesystem may transition to a mode for heating the entire build chamber toits desired build chamber temperature. This latter step may beaccomplished by increasing the flow rate of air in order to morevigorously mix and temper air throughout the build chamber.

The desired build region temperature and the desired build chambertemperature may be predetermined temperatures based on, for example, thetype of build material being used in a three-dimensional printingsystem. The desired build region temperature and the desired buildchamber temperature may be the same temperature, or these may bedifferent temperatures. Determining the desired temperature may includefirst identifying parameters for heating the build chamber and/oridentifying parameters for changing the heating environment during abuild process.

For example, the predetermined temperature for preheating the buildregion may be about 60° C., which may be a preferred temperature for thebuild region when extruding polylactic acid (PLA) or some other buildmaterial in a three-dimensional printing process. Other materials mayhave different useful operating ranges. Thus, for example, the buildregion might usefully be preheated to a higher temperature such as about65-70° for acrylonitrile butadiene styrene (ABS) or the like. Thepredetermined temperature may also include even higher temperatures. Forexample, the predetermined temperature may be close to or equal to theglass transition temperature of the build material (e.g., 110° C. forABS). Moreover, the predetermined temperature may be lower than 60° C.The predetermined temperature may provide a threshold for starting abuild, so that the build is initiated only when the build region reachesthe predetermined temperature. Similarly, when the build region is belowthe predetermined temperature, such as when a printer is powered on orfollowing a prolonged pause in printing activity, a build may begin witha preheating step in which the build region is heated up to thepredetermined temperature. The heater and blower described herein canreduce the wait time required to heat the build region, as distinguishedfrom the build chamber generally, by directing heated air slowly overthe heater and the build region.

In one aspect, a three-dimensional printer may include a heater such asany of the heaters described above, along with a blower configured tomove air at a variable flow rate in response to a control signal. Asnoted above, a lower flow rate may be used to more quickly heat thebuild region, while a higher flow rate may be used to generally heat thebuild chamber. A controller may control operation of the printer as itmoves from the preheat mode to the build chamber heating mode asdescribed herein. The controller may provide the control signal based inwhole or in part on a sensor signal received from a sensor such as athermistor that provides a sensor signal indicative of a temperaturewithin the build volume. For example, the sensor may be positioned todirectly measure the temperature of the build region where a build is tobe initiated, or to more generally measure a temperature at any suitablelocation within the build chamber from which a temperature of the buildregion can be inferred. In one aspect, the control signal may drive theblower at a first speed (to obtain a first flow rate) used to preheatthe build region before initiating the build and at a second speed (toobtain a second flow rate) to heat the entire build chamber afterinitiating the build. As noted above, the second flow rate may begreater than the first flow rate.

Thus, in the implementations depicted in FIGS. 3 and 4, the blower 316,416 moving air over the coil heaters 314, 414 at a reduced flow rate mayheat the build region more quickly than the blower 316, 416 moving airover the coil heaters 314, 414 at an increased flow rate. As discussedabove, this heating behavior is generally improved by the tendency ofheated air to rise, and the improved heat transfer to and from theheated air that is possible at lower flow rates. One of ordinary skillwill appreciate that other control techniques are possible, such asusing a second flow rate less than the first flow rate, or flow rates inboth modes that vary over time.

As shown in FIG. 4, the blower 416 may include a fan 420, and the firstflow rate and the second flow rate may be determined by a rotationalspeed of the fan 420. For example, in order to move air at the firstflow rate, the fan 420 may have a first rotational speed, and in orderto move air at the second flow rate, the fan 420 may have a secondrotational speed, where the second rotational speed may be greater thanthe first rotational speed.

The sensor may be a temperature sensor, which, for example, may be athermistor, infrared sensor, infrared camera, or other thermallysensitive device. The sensor may be located and configured such that itsenses the temperature in the build region, in a region adjacent to theheater, or anywhere else in the build chamber where build chamber andbuild region temperatures can be directly measured or accuratelyinferred. The device may also include a plurality of sensors such as afirst sensor to measure the build region temperature and a second sensorto measure a build chamber temperature. This may also include multiplesensors to take sensors at different locations used to determine anaverage temperature, e.g., for the build region or the build chamber.The sensor may also or instead include a flow rate sensor that sensesthe flow rate of air from the blower, and the sensor signal may includethe flow rate of air in the build chamber. In an embodiment where theblower includes a fan, the sensor may also or instead include arotational speed sensor, and the sensor signal may include a rotationalspeed of the fan. In another aspect, fan speed and corresponding flowrates may be inferred by a voltage or current applied to a fan motor.

In order to control the build chamber temperature and/or the temperatureof the build region, the heater may also or instead be configured toprovide variable heat in response to a heat control signal. Thecontroller may be configured to vary the heat control signal in responseto the sensor signal. This may usefully include adjusting the suppliedheat as the flow rate of air over the heater changes in any suitablemanner to achieve a desired heat transfer.

There may be a predetermined standard operating flow rate forcirculating air in the build chamber of a three-dimensional printer. Inan implementation, after the build region is heated to the desired buildregion temperature, the blower may adjust a flow rate to thepredetermined standard operating flow rate. For example, the second flowrate may be equal to the predetermined standard operating flow rate,such that the blower moves air the first flow rate to preheat the buildregion before initiating the build, and at the predetermined standardoperating flow rate to circulate air in the build chamber afterinitiating the build. The standard operating flow rate may cause thebuild chamber to reach a substantially uniform temperature, or otherwisedistribute heat in the build chamber. The standard operating flow ratemay also or instead mix the air in the build chamber in a desiredmanner.

In addition to varying the control signal to drive the blower at thefirst and second flow rates, the controller may also be configured toinitiate the build when the build region is heated to the predeterminedtemperature. In other words, the controller may send a build signal tothe three-dimensional printer to initiate the build. This build signalmay be sent in response to the sensor signal provided to the controller.

The flow rate of the blower may be increased (e.g., from the first flowrate to the second flow rate) after the build is initiated, which may beat any time after the build is initiated—for example, during fabricationof a first layer of the build, after fabrication of a first layer of thebuild, after a specified time, after a specified volume of buildmaterial has been extruded, when the build has moved out of a specifiedvolume where the build was initiated, when the build region has movedout of an air path of the blower, and so on.

A method for controlling a build chamber temperature of athree-dimensional printer will now be described.

FIG. 5 illustrates a method 500 for controlling a build chambertemperature of a three-dimensional printer, where step 502 includesdetermining a predetermined temperature for initiating a build in abuild region of a build chamber of a three-dimensional printer (e.g.,the desired build region temperature). Step 504 includes preheating thebuild region to the predetermined temperature, which may be achieved bydirecting air with a blower at a first flow rate 510 over a heater andtoward the build region. This may include sensing a temperature of thebuild region with a sensor such as any of the sensors described above.Step 506 includes initiating the build when the build region reaches thepredetermined temperature. Lastly, step 508 includes heating the buildchamber, which may be achieved by directing air with the blower at asecond flow rate 512 over the heater. The second flow rate may begreater than the first flow rate. The build chamber may be heated afterthe build region reaches the predetermined temperature, after a buildhas been initiated, after a build region has moved out of a direct pathof the blower, or at any other suitable time.

As noted above, the heater may also provide a variable, controllableoutput, and the method 500 may include varying a heat output from theheater at any suitable time(s) during a build process, or in response toany suitable criteria such as a heated air temperature, a targettemperature for the build chamber, a target temperature for the buildregion, and so forth.

FIG. 6 is a block diagram illustrating a temperature control system. Asshown in FIG. 6, a build chamber 600 of a three-dimensional printer mayinclude a build region 602. This may include any region where a buildmay be initiated, such as a particular location on a build platform, anentire build platform, a volume around an extrusion tool, or any otheruseful volume or location for initiating a build. A heater 604 mayprovide heat, and a blower 606 may move air at a variable flow rate inresponse to a blower control signal 608 from a controller 610. Theheater 604 may also provide variable heat in response to a heatercontrol signal 612 from the controller 610. The blower 606 may bepositioned to move unheated air 614 over the heater 604, which thencreates heated air 616 that may be moved toward the build region 602(e.g., by the blower 606 or due to heated air rising vertically withinthe build chamber or some combination of these) in order to heat thebuild region 602 to a predetermined temperature. A sensor 618 mayprovide a sensor signal 620 indicative of a temperature of the buildregion 602. The controller 610 may then vary one or more of the controlsignals 608, 612 in response to the sensor signal 620. The blowercontrol signal 608 may drive the blower 606 at a first flow rate topreheat the build region 602 before initiating the build, and the blowercontrol signal 608 may drive the blower 606 at a second flow rate, whichmay be greater than the first flow rate, to heat the build chamber 600after initiating the build. The heater control signal 612 may vary theheat output of the heater 604 to either heat up or cool down the buildregion 602 and/or build chamber 600.

According to the foregoing, disclosed herein there is athree-dimensional printer configured to rapidly heat a build regionwithin a build chamber to a predetermined printing temperature, and thenmaintain a target temperature for an entire volume of the build chamberafter the build has been initiated. This may include using a blower witha fan or the like that blows air across a heater and through the buildregion at a low flow rate during a preheat of the build region to afirst predetermined temperature, and at a higher flow rate to circulateair and maintain the build chamber at a second predetermined temperatureafter the build has been initiated. The blower flow rate may beincreased, e.g., after the first layer of the build is completed, aftera predetermined time, after the build region has moved out of a flowpath of the blower, after the build region reaches the firstpredetermined temperature, after the build is initiated, after the buildchamber reaches the second predetermined temperature, or at any othersuitable time that can be determined by the controller. In anembodiment, the air distribution and temperature distribution across thebuild chamber may be monitored with sensors, which may be incommunication with a controller that sends a control signal to at leastone of the blower and the heater.

The blower and heater may also be used after initiation of the build ina control loop with any number of temperature sensors to maintain atemperature of the build chamber at a predetermined target temperature.An implementation may also include cooling the build chamber, e.g., ifthe build chamber exceeds a maximum temperature. For example, the heatermay be turned completely off, and the blower may move air in the buildchamber in order to cool the build chamber. Where more rapid cooling isdesired, active cooling elements may be employed, or an exhaust vent orthe like may be provided to exchange heated air within the build chamberwith cooler ambient air. In an embodiment, a sensor may constantlymonitor the temperature of the build region and/or the build chamber,and the flow rate of the blower may be continuously adjusted, oradjusted according to the constantly monitored temperature.

As discussed herein, the devices and methods may involve determining adesired build region temperature for initiating a build in the buildregion of the build chamber of a three-dimensional printer, andidentifying parameters for determining the desired build regiontemperature. Such parameters may include, but are not limited to, thebuild material, the build size (surface area, volume, density, etc.),geometry, time, printing schedule, and so on. Additionally, animplementation includes a system and method for limiting build chamberheating based on the size and geometry of the build. For example, if abuild is below a predetermined size, the build chamber is not be heated.

The devices and methods described herein may be implemented throughcomputer software (as explained below), and may include a control systemthat automatically controls the temperature and/or flow rate of airthroughout the build chamber. This may include an implementation wherethe control signal is generated by a computer program. Thus, animplementation may include a device and method that does not include asensor. Alternatively, the control system may include a feedback systemthat uses at least one sensor as described herein. For example, thecontrol system may adjust the temperature of the build chamber and/orbuild region based on a sensed temperature (e.g., by sending a controlsignal to vary the flow rate of the blower or the heat output of theheater). For example, the control scheme for the blower may use aswitched mode power supply (SMPS) (e.g., a buck converter). The controlsystem may also or instead utilize pulse-width modulation (PWM) control,pulse-duration modulation (PDM) control, thermostatic control, linearvoltage regulation, resistors, diodes, volt modding, manual fan speedcontrol, software control, and so on, in order to control the blower,heater, or any other component of a three-dimensional printing system.

An implementation utilizing PWM control with separate heater sectionswill now be described. The heater in an implementation may include atleast two separate heater sections such that the heater is not operatedfrom a single electronics output device. Further, the separate heatersections may be driven independently from one another. The amount ofheat produced from the separate heater sections may be controlled with aPWM scheme, which may switch the heaters off and on at a substantiallyhigh frequency and may vary the duty cycle (on time versus off time).The heater being broken up into at least two separate and independentlycontrollable sections may allow for intelligent PWM control of theseparate heater sections in a synchronized or complementary fashion. Forexample, the heaters may be operated at a 50% duty cycle (50% of thetime the heaters are on, and 50% of the time the heaters are off), whichmay be accomplished through turning the at least two heater sections onat the same time and then off at the same time. Alternatively, it maybenefit the power supply if the separate heater sections are driven 180degrees out of phase. Out of phase operation may effectively spread outthe power demanded from the power supply, which may be beneficial over alarge instantaneous power demand. For example, the spreading of powerdemand may benefit electrical components within the power supply byreducing the peak power seen by the electrical components. This mayextend the power supply lifetime. Thus, it may be advantageous to breakup a large electrical heater load into separate smaller sections andintelligently drive them with a PWM scheme, which may place the heaterdrive sections out of phase with one another. This drive scheme mayreduce strain on an associated DC power supply stage by reducing peakcurrent and peak power demand, which may increase the projected powersupply lifetime.

The above systems, devices, methods, processes, and the like may berealized in hardware, software, or any combination of these suitable forthe control, data acquisition, and data processing described herein.This includes realization in one or more microprocessors,microcontrollers, embedded microcontrollers, programmable digital signalprocessors or other programmable devices or processing circuitry, alongwith internal and/or external memory. This may also, or instead, includeone or more application specific integrated circuits, programmable gatearrays, programmable array logic components, or any other device ordevices that may be configured to process electronic signals. It willfurther be appreciated that a realization of the processes or devicesdescribed above may include computer-executable code created using astructured programming language such as C, an object orientedprogramming language such as C++, or any other high-level or low-levelprogramming language (including assembly languages, hardware descriptionlanguages, and database programming languages and technologies) that maybe stored, compiled or interpreted to run on one of the above devices,as well as heterogeneous combinations of processors, processorarchitectures, or combinations of different hardware and software. Atthe same time, processing may be distributed across devices such as thevarious systems described above, or all of the functionality may beintegrated into a dedicated, standalone device. All such permutationsand combinations are intended to fall within the scope of the presentdisclosure.

Embodiments disclosed herein may include computer program productscomprising computer-executable code or computer-usable code that, whenexecuting on one or more computing devices, performs any and/or all ofthe steps of the control systems described above. The code may be storedin a non-transitory fashion in a computer memory, which may be a memoryfrom which the program executes (such as random access memory associatedwith a processor), or a storage device such as a disk drive, flashmemory or any other optical, electromagnetic, magnetic, infrared orother device or combination of devices. In another aspect, any of thecontrol systems described above may be embodied in any suitabletransmission or propagation medium carrying computer-executable codeand/or any inputs or outputs from same.

The method steps of the invention(s) described herein are intended toinclude any suitable method of causing one or more other parties orentities to perform the steps, consistent with the patentability of thefollowing claims, unless a different meaning is expressly provided orotherwise clear from the context. Such parties or entities need not beunder the direction or control of any other party or entity, and neednot be located within a particular jurisdiction.

It will be appreciated that the methods and systems described above areset forth by way of example and not of limitation. Numerous variations,additions, omissions, and other modifications will be apparent to one ofordinary skill in the art. In addition, the order or presentation ofmethod steps in the description and drawings above is not intended torequire this order of performing the recited steps unless a particularorder is expressly required or otherwise clear from the context. Thus,while particular embodiments have been shown and described, it will beapparent to those skilled in the art that various changes andmodifications in form and details may be made therein without departingfrom the spirit and scope of this disclosure and are intended to form apart of the invention as defined by the following claims, which are tobe interpreted in the broadest sense allowable by law.

What is claimed is:
 1. A system comprising: a build chamber of athree-dimensional printer; a heater configured to heat the buildchamber, the heater including at least two separate and independentlycontrollable heating elements; a power source configured to supply powerto the heater; and a controller configured to provide pulse-widthmodulation (PWM) control of the heating elements in a manner thatstaggers an on-cycle among the heating elements to reduce a peak loaddemand on the power source.
 2. The system of claim 1 wherein thecontroller is configured to switch the heating elements off and on in asynchronized fashion.
 3. The system of claim 1 wherein the controller isconfigured to switch the heating elements off and on in a complementaryfashion.
 4. The system of claim 1 wherein the controller is configuredto vary a duty cycle of the heating elements.
 5. The system of claim 1wherein the controller is configured to allocate 50% of a predeterminedduty cycle to the at least two separate heating elements.
 6. The systemof claim 5 wherein the predetermined duty cycle is a duty cycle requiredto drive one of the at least two separate heating elements at apredetermined power.
 7. The system of claim 1 wherein the controller isconfigured to operate one of the at least two heating elements out ofphase with another one of the at least two heating elements.
 8. Thesystem of claim 7 wherein the heating elements are operated 180 degreesout of phase.
 9. The system of claim 7 wherein the heater includes Nseparate and independently controllable heating elements, and whereinthe heating elements are operated 360/N degrees out of phase therebyevenly distributing operation of the heating elements.
 10. The system ofclaim 1 wherein the heating elements are coil heaters.
 11. The system ofclaim 1 wherein the power source is an electronic power supply, andwherein reducing the peak load demand on the power source increases aprojected lifetime of the electronic power supply.
 12. A methodcomprising: providing a heater including at least two separate andindependently controllable heating elements, the heater configured toheat a build chamber of a three-dimensional printer, and the heaterpowered by a power source; and independently driving the at least twoheating elements using a pulse-width modulation (PWM) control schemeimplemented by a controller, the PWM control scheme staggering anon-cycle among the heating elements to reduce a peak load demand on thepower source.
 13. The method of claim 12 further comprising switchingthe heating elements off and on in a synchronized fashion.
 14. Themethod of claim 12 further comprising switching the heating elements offand on in a complementary fashion.
 15. The method of claim 12 furthercomprising varying a duty cycle of the heating elements.
 16. The methodof claim 12 further comprising determining a duty cycle to operate oneof the at least two heating elements at a predetermined power, andallocating 50% of the duty cycle to the at least two heating elements.17. The method of claim 12 further comprising operating one of the atleast two heating elements out of phase with another one of the at leasttwo heating elements.
 18. The method of claim 17 further comprisingoperating the heating elements 180 degrees out of phase.
 19. The methodof claim 17 further comprising operating the heating elements 360/Ndegrees out of phase, wherein the heater includes N separate andindependently controllable heating elements.
 20. The method of claim 12further comprising varying a heat output from the heating elementsaccording to a target temperature for the build chamber.